This tutorial will demonstrate how to utilize the serial port on Raspberry Pi. The Raspberry will utilize the serial port using both an RS232/TTL 3-5,5V adapter and a USB-serial adapter. The Raspberry Pi’s serial port is set up for console input/output as the default configuration. This can be useful for troubleshooting boot issues or accessing the Pi when video and network are unavailable.
In order to communicate with other devices like modems or printers using the serial port, it is necessary to turn off the console login for the serial port.
In this setup, we utilize a Raspberry Pi 2 and link an RS232/TTL 3-5.5V converter to pins 4 (5V), 6 (GND), 8 (TX), and 10 (RX) of the Raspberry Pi, ensuring to connect TX with RX and vice versa.
To search for available serial ports we use the command
dmesg | grep tty
The output is something like this
pi@raspberrypi ~ $ dmesg | grep tty [ 0.000000] Kernel command line: dma.dmachans=0x7f35 bcm2708_fb.fbwidth=656 bcm2708_fb.fbheight=416 bcm2709.boardrev=0xa01041 bcm2709.serial=0x93f9c7f9 smsc95xx.macaddr=B8:27:EB:F9:C7:F9 bcm2708_fb.fbswap=1 bcm2709.disk_led_gpio=47 bcm2709.disk_led_active_low=0 sdhci-bcm2708.emmc_clock_freq=250000000 vc_mem.mem_base=0x3dc00000 vc_mem.mem_size=0x3f000000 dwc_otg.lpm_enable=0 console=tty1 console=ttyAMA0,115200 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait [ 0.001774] console [tty1] enabled [ 0.749509] dev:f1: ttyAMA0 at MMIO 0x3f201000 (irq = 83, base_baud = 0) is a PL011 rev3 [ 1.268971] console [ttyAMA0] enabled pi@raspberrypi ~ $
Last line indicates that the console is enabled on the serial port ttyAMA0, so we disable it
Run the configuration command and follow the instructions below
sudo raspi-config
Reboot and try with
dmesg | grep tty
output now is
pi@raspberrypi ~ $ dmesg | grep tty [ 0.000000] Kernel command line: dma.dmachans=0x7f35 bcm2708_fb.fbwidth=656 bcm2708_fb.fbheight=416 bcm2709.boardrev=0xa01041 bcm2709.serial=0x93f9c7f9 smsc95xx.macaddr=B8:27:EB:F9:C7:F9 bcm2708_fb.fbswap=1 bcm2709.disk_led_gpio=47 bcm2709.disk_led_active_low=0 sdhci-bcm2708.emmc_clock_freq=250000000 vc_mem.mem_base=0x3dc00000 vc_mem.mem_size=0x3f000000 dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait [ 0.001769] console [tty1] enabled [ 0.749438] dev:f1: ttyAMA0 at MMIO 0x3f201000 (irq = 83, base_baud = 0) is a PL011 rev3 pi@raspberrypi ~ $
Now we can use the serial ttyAMA0. We connect an adapter usb / serial, then we will try to establish a communication between the two serial ports; obviously in a practical application to every serial we could connect a device, for example a modem, a printer a RFID reader etc.
For more detail: Read and write from serial port with Raspberry Pi
